I want to start a project that uses the magic loop. I've avoided that method (as in never did it). I think that I understand HOW to do it, but my question is WHY? What is the advantage and can I just knit in the round or use DPN?
You can certainly knit in the round on dpns depending on how many sts you need to work with. Magic loop is a great technique to use if you don't like dpns since you can work small diameter circular projects on just the one large circular needle. It's a matter of preference.
The advantage (at least for me) is that I only need to buy *one* needle in a given size. BTW, I'm a new knitter, only learned in May of this year. So...I have a #3 x 47, #4 x 60", #5 x 60", #6 x 32" and #6 x 60" (the 32" was for a class but I couldn't stand how crowded and curled-up the sts were), etc.
One circ in each size has begun to impose its own discipline w/regard to the number of projects in progress, too. Which is a good thing; ask me how many quilts in progress I have....
Some people, like me, don't like using dpns, and prefer to knit on circs. Also, if you knit a hat, you need a 16" to start with, but then have to switch to dpns after beginning the decreases as the sts won't fit on it anymore. If you use a longer circ for the hat you don't have to switch needles, just do single or magic loop from start to finish.
I like magic loop b/c personally I feel like it is easier to put my knitting down and pick it up again without losing stitches. Also, magic loop can be used to make things 2 at a time like socks and mittens